1. Field
The disclosure relates to an electric vehicle and, in particular, to an electric vehicle that includes a motor for traveling, an inverter that drives this motor, and a cooler that cools the inverter.
2. Description of Related Art
As an electric vehicle of this type, an electric vehicle that limits a load factor of a motor at a time when an element temperature of an inverter that drives the motor exceeds a threshold has conventionally been suggested (for example, see International Publication No. 2012/124073). In this electric vehicle, the threshold at a time when limitation is applied to the load factor of the motor is changed by using a temperature of a cooling liquid of a cooler that cools the inverter, a DC voltage applied to the inverter, a carrier frequency, and the like as parameters. In this way, performance of the inverter can sufficiently be exhibited.
In the above-described electric vehicle, the load factor of the motor is limited. However, depending on a rotational speed of the motor, there is a case where a current flows through the inverter and the element temperature of the inverter is increased. When the motor rotates at a relatively high rotational speed, an induced voltage generated by the motor (also referred to as a counter-electromotive voltage) becomes higher than the DC voltage input to the inverter. Thus, field-weakening control is typically executed. When the field-weakening control is executed, the current flows through the inverter, and the element temperature of the inverter is increased. In particular, when abnormality occurs to the cooler that cools the inverter, the element temperature of the inverter is abruptly increased. Thus, the limitation of the load factor of the motor is not sufficient enough to prevent overheating of the inverter.